Annihilating Aura. Any creature that starts its turn with in 40 feet of the nightcrawler must succeed on a DC 22 Constitution saving throw or take 21 (6d6) necrotic damage and grant the nightcrawler advantage on attack rolls against it until the start of the creature's next turn. Undead are immune to this aura.

Life Eater. A creature reduced to 0 hit points from damage dealt by the nightcrawler dies and can't be revived by any means short of a wish spell.

Enervating Maw. Melee Weapon Attack: +16 to hit, reach 5 ft., one target. Hit: 31 (5d8 + 9) necrotic damage. If the target is a Large or smaller creature, it must succeed on a DC 19 Dexterity saving throw or be swallowed by the nightcrawler. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the nightcrawler, and it takes 21 (6d6) necrotic damage at the start of each of the nightcrawler's turns. Each time the target takes necrotic damage, it must succeed on a DC 22 Constitution saving throw or its hit point maximum is reduced by an amount equal to the necrotic damage taken. This reduction lasts until the target finishes a long rest.

 If the nightcrawler takes 20 damage or more on a single turn from a creature inside it, the nightcrawler must succeed on a DC 24 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the nightcrawler. If the nightcrawler dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 5 feet of movement, exiting prone.

Finger of Doom (Recharge 6). The nightcrawler chooses one creature it can see within 300 feet of it. The target must succeed on a DC 22 Wisdom saving throw or take 32 (5d12) necrotic damage and become frightened until the end of the nightcrawler's next turn. While frightened in this way, the creature is paralyzed. If a target's saving throw is successful, the target is immune to the nightcrawler's Finger of Doom for the next 24 hours.